A Handy Guide to Figuring Out Blurs in Photoshop

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Blurs can be beautiful things. They can hide imperfections or soften an image. They can help in the background to draw attention to what you want your viewer to see. Or, they can help you blur a background to see some text. Once you decide to add a blur, you'll quickly realize that there are a bunch of different kinds blurs in Photoshop.
Blurs can be accessed from the Filter menu. You have 14 different options available to you. We'll be discussing the last 11 blurs in the Filter menu in this article. Keep on the lookout for part two, which will cover the other three blurs as well as the Blur Tool.
Different blurs should be used in different instances. A motion blur, for example, would be great on something that you want to show movement to, like a car or skateboard. But if you just want to blur a background a motion blur might be the wrong way to go. We’re going to use the same photo in all of our examples so that you can really see what the blur is doing, rather than focusing on a subject. It’ll be easier to see the differences in blur type if you’re always seeing it applied to the same image. Please note, however, that while we’ll show you a blur on an image, it doesn’t mean that that’s necessarily the best blur to use for that particular image.
We'll be using this image of tulips for all of the blur examples.

Image by flickr user James Wheeler CC by SA 2.0

Average Blur

Selecting this option will create a color that’s the average of all the colors in your image by averaging the color value of neighboring pixels. If you just simply select Average Blur, your image will turn one color. The Average Blur added to our tulip image is displayed below.

If you haven’t made any selections, like with the Lasso tool, then the Average Blur will replace your entire image with the entire image’s average.

However, if you’d like you can select one area, before choosing Average Blur, and then it’ll replace that area with the average color that’s in that selection. By using a selection tool, you’ll be able to smooth out one area of color.

A helpful way to use this blur is to get a more correct color in your image by removing a color cast. First, make sure you make a duplicate of your image. Select Average blur then add an adjustment layer to it. Choose the Levels option. Then select the gray eyedropper and click on your image. You should see the entire image turn gray.

Now, if you hide the layer that’s holding the average blur (the new gray layer), you’ll have a color-corrected image, as you can see in the image below. (Hover over the image below to produce a slider. Use the slider to slide back and forth between versions. The image on the left is the original and the image on the right is color corrected using Average Blur.)

Blur and Blur More

The Blur Filter will look for significant color transition or edges. The way that this blur works is by blurring significant color transitions together. There are no controls available for this filter. The option under Blur in the Filters menu is Blur More. Blur More is a way that you can create a more blurry image once you’ve used the Blur filter. Every time you select Blur More, it will blur the image around 3 to 4 times more than it was originally blurred.

If you’re working with a high resolution image, you’ll need to click blur much more often to achieve a hazy image. Lower resolution images will create a much more pronounced effect. In the image below, we’ve used the Blur filter and clicked Blur More 10 times.

See how it’s still not very blurry or hazy? If you’re going for a significant blur, then the Blur and Blur More filters probably aren’t the best way to go.

Box Blur

The Box Blur Filter uses an average color average of nearby color values to blur an image. Because of this, it’s got more control than the Blur Filter. It looks for edges within an image. Two contrasting colors that are right next to each other will create an edge. A box blur can retain more of the definition in an image.

The edges of the shapes will still be a little defined, but it can also create some distortion. Since it can create a weird distortion, it’s usually used for special effects.

You can use this blur only to a selected area if you’d like.

Gaussian Blur

The Gaussian Blur Filter will blur an image or selected area by an adjustable amount based upon a weighted average. The end result of a Gaussian blur is a hazy effect. Not to get into math, but the way that this blur works is through the Gaussian function that tells the radius what to do.

With the Gaussian Blur, you’re able to make a few different choices in order to get a look that you’re going for. You’re able to choose the Radius and the Threshold.

The smaller the radius, the less blur you’ll get. This blur is more evenly distributed and doesn’t create weird shapes at edges and fine points like the Box Blur can. It’s a great way to bring focus to part of an image by making a section and blurring outside of it.

Lens Blur

Using the Lens Blur Filter can gives the illusion of a narrower depth of field on your image. This blur works based upon a depth map. You can easily create a depth map by creating an alpha mask. There are a lot of different ways to do this.

We’re going to show you a simple way to get started with using this blur effectively. What you’ll need to do first is add a new Channel to your image. The Channels panel is within the Layers panel. Move on over there and add a new channel. By default, your new Channel will be called Alpha 1 and will be completely black. You can apply a simple gradient to create a depth of field to your Alpha Channel.

After this Channel is created, you should click on your RGB Channel to turn it back on and turn the Alpha Channel off. Make sure you’ve selected the RGB Channel, or the next steps won’t work properly.

Now, switch back over to your layers panel and be sure that the layer you’re working on is selected. Select Lens Blur from the Filter menu. A pretty good sized dialog box will appear.

Under Depth Map there should be a drop down menu called Source. Choose your Alpha Channel from there. If you’ve put the black part of your gradient where you want the image to be in focus you can move on to the next step. If you’ve put the black part of the gradient where you’d like the blur to not be, just simply click the invert button.

You can change the Radius of the blur to control how blurry your image will be in the background. Press OK and you’ll have an image that gives that narrow depth of field illusion.

Motion Blur

The Motion Blur Filter applies a specific blur in a specific direction with a specific intensity to your image. The image below has a vertical Motion Blur applied to it.

A dialog box will open with a couple options for you, including a little wheel.

The wheel will let you choose the direction of the blur by rotating it around. And then you can choose the distance that you’d like the image to be blurred. So if you want just a little blur, you’d pick a small amount. You can also just select a part of the image to blur. Selecting just a part of the image to blur will help to really create the illusion that your subject was moving. Below is an example of a vertical Motion Blur.

Radial Blur

A Radial Blur will simulate either zooming in or rotating a camera. The Radial Blur is a little different from the previous blurs, since there’s not a way for you to really preview your work on your actual image. A dialog box will appear and you’ll have to make your selections without seeing it directly on your image.

The quality setting controls the amount of grain that you’ll see after the filter is applied. The Amount setting controls how much blur you’ll be able to see, so a lower amount equals a lower blur.

You can change the center of the blur within the dialog box as well. The only way you’ll be able to guess how your image will look is in the white part of the dialog box.

The Spin Blur Method will create a rotating camera effect, like you see below. The Zoom Blur Method will create a zooming effect.

Shape Blur

You can create a blur based upon a vector shape. In Shape Blur dialog you’ll be able to choose one of the shapes that are already included within Photoshop. You can also add a custom shape to base the blur upon.

The Shape Blur might be best to use on simple shapes, and only part of your image. We’ve selected the circle shape and added it to our tulips image, just to show you the effect.

Smart Blur

The Smart Blur smooths out grain and noise patterns between edges (where two contrasting colors border each other). So if you’ve got a particularly grainy image, this filter can help you smooth it out.

The Smart Blur dialog box gives you quite a bit of control on your blur. There’s not a preview check box available, but there’s still a good-sized window for you to look at.

The Threshold Setting will tell Photoshop how different the pixels need to be before they’re blurred. If you want a very minimal change, choose the lowest setting.

The Quality setting will change, you guessed it, the quality of the blur. The Mode setting will let you see where Photoshop is detecting edges.

Surface Blur

The Surface Blur filter blurs the image with the exception of the edges. You are able to control both the Radius and Threshold with this Blur filter. A high radius will cause you to lose a lot of detail in your image. The Threshold will allow Photoshop to look at the pixels in the radius and figure out how they should be blurred. Surface Blur is a great way to smooth out skin in an image.

However, without some additional steps, using this filter can smooth out too much detail and texture and make your image look fake.

If you add a layer mask to your layer and use your brush tool with the mask selected you can get some of the detail you might want back. If you brush over with black in the areas that you want to bring back some of the detail you can keep some of the smoothing that you were wanting, while making your image look much more real.

Now that you know more about some of the blurs in Photoshop, try testing your overall Photoshop knowledge with a free test from our friends over at Smarterer.